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United States Patent |
6,119,208
|
White
,   et al.
|
September 12, 2000
|
MVS device backup system for a data processor using a data storage
subsystem snapshot copy capability
Abstract
The MVS device backup system functions to enable the data processor to
manage the device backup function of a disk data storage subsystem in a
manner that minimizes the expenditure of data processor resources. This is
accomplished by the MVS device backup system determining the source device
volume on the data storage subsystem, the target device volume on the data
storage subsystem and identifying the extent of both. The MVS device
backup system then transmits data to the data storage subsystem,
representative of the assignment of DASD full tracks from the source
device location on the data storage subsystem as well as DASD full tracks
from the target (backup) device location on the data storage subsystem.
The data processor based MVS device backup system then uses ECAM channel
programs to instruct the data storage subsystem to perform the device
backup operation using snapshot track pointer copy operations. Upon
conclusion of the device backup operation by the data storage subsystem,
the MVS device backup system updates the meta data required to complete
the device backup operation.
Inventors:
|
White; Michael Wayne (Lafayette, CO);
Tomsula; Patrick James (Arvada, CO)
|
Assignee:
|
Storage Technology Corporation (Louisville, CO)
|
Appl. No.:
|
844480 |
Filed:
|
April 18, 1997 |
Current U.S. Class: |
711/162; 711/111; 711/112; 711/161 |
Intern'l Class: |
G06F 013/00; G06F 012/00 |
Field of Search: |
711/161,162,111,112
|
References Cited
U.S. Patent Documents
5212784 | May., 1993 | Sparks | 395/575.
|
5255270 | Oct., 1993 | Yanai et al. | 371/10.
|
5276860 | Jan., 1994 | Fortier et al. | 395/575.
|
5630092 | May., 1997 | Carreiro et al. | 395/438.
|
5649152 | Jul., 1997 | Ohran et al. | 395/441.
|
Foreign Patent Documents |
0 566 967 A2 | Oct., 1993 | EP | .
|
0 767 431 A1 | Apr., 1997 | EP | .
|
Primary Examiner: Cabeca; John W.
Assistant Examiner: Thai; Tuan V.
Attorney, Agent or Firm: Duft, Graziano & Forest, P.C.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is related to copending applications titled "System For
Providing Write Notification During Data Set Copy" and "DASD File Copy
System For A Data Processor Using A Data Storage Subsystem Snapshot Copy
Capability", filed on the same date as the present invention, Ser. No.
08/843,544 (now U.S. Pat. No. 5,915,264) and Ser. No. 08/844,046 (now
pending), respectively.
Claims
What is claimed:
1. A device backup apparatus for the copying of of a selected data storage
device which is stored on a dynamically mapped virtual memory data storage
subsystem having a rewriteable memory space, which device backup apparatus
is extant on a data processor connected to the data storage subsystem
which is operational to instantaneously create a copy of a selected device
independent of said data processor, said device backup apparatus
comprising:
means for allocating memory in said rewriteable memory space for a selected
device written thereon as well as for a copy of said selected device;
means for transmitting control messages to said data storage subsystem to
identify all data sets which comprise said selected device, and memory
space for said copy of said selected device;
means for activating said data storage subsystem to implement said
instantaneous copy operation on said identified all said data sets which
comprise said selected device; and
means, responsive to said data storage subsystem copying said selected
device, for updating meta data associated with a copy of said selected
device created by said data storage subsystem, which metadata is known by
said data processor.
2. The device backup apparatus of claim 1 wherein said means for allocating
memory comprises:
means for determining a location and an extent of said selected device.
3. The device backup apparatus of claim 1 wherein said means for allocating
memory comprises:
means for determining a location and an extent of said copy of said
selected device.
4. The device backup apparatus of claim 1 wherein said means for
transmitting control messages comprises:
means for transmitting data to said data storage subsystem to identify a
location and an extent of said selected device, and a location and an
extent for said copy of said selected device.
5. A device backup apparatus for the copying of of a selected data storage
device which is stored on a dynamically mapped virtual memory data storage
subsystem having a rewriteable memory space, which device backup apparatus
is extant on a data processor connected to the data storage subsystem
which is operational to instantaneously create a copy of a selected device
independent of said data processor, said device backup apparatus
comprising:
means for allocating memory in said rewriteable memory space for a selected
device written thereon as well as for a copy of said selected device;
means for transmitting control messages to said data storage subsystem to
identify all data sets which comprise said selected device, and memory
space for said copy of said selected device;
means for activating said data storage subsystem to implement said
instantaneous copy operation on said identified all said data sets which
comprise said selected device; and
means, responsive to said data storage subsystem copying said selected
device, for updating meta data associated with a copy of said selected
device created by said data storage subsystem, which metadata is known by
said data processor, comprising:
means for updating at least one of device meta data comprising:
VTOC; Volume labels; VTOC index; VVDS data.
6. The device backup apparatus of claim 5 wherein said means for allocating
memory comprises:
means for determining a location and an extent of said selected device.
7. The device backup apparatus of claim 5 wherein said means for allocating
memory comprises:
means for determining a location and an extent of said copy of said
selected device.
8. The device backup apparatus of claim 5 wherein said means for
transmitting control messages comprises:
means for transmitting data to said data storage subsystem to identify a
location and an extent of said selected device, and a location and an
extent for said copy of said selected device.
9. A device backup method for the copying of a selected data storage device
which is stored on a dynamically mapped virtual memory data storage
subsystem having a rewriteable memory space, which device backup method is
extant on a data processor connected to the data storage subsystem which
is operational to instantaneously create a copy of a selected device
independent of said data processor, said device backup method comprising
the steps of:
allocating memory in said rewriteable memory space for a selected device
written thereon as well as for a copy of said selected device;
transmitting control messages to said data storage subsystem to identify
said selected device, and memory space for said copy of said selected
device;
activating said data storage subsystem to implement said instantaneous copy
operation on said identified all data sets which comprise said selected
device; and
updating, in response to said data storage subsystem copying said selected
device, meta data associated with said device and known by said data
processor.
10. The device backup method of claim 9 wherein said step of allocating
memory comprises:
determining a location and an extent of said selected device.
11. The device backup method of claim 9 wherein said step of allocating
memory comprises:
determining a location and an extent of said copy of said selected device.
12. The device backup method of claim 9 wherein said step of transmitting
control messages comprises:
transmitting data to said data storage subsystem to identify a location and
an extent of said selected device, and a location and an extent for said
copy of said selected device.
13. A device backup method for the copying of a selected data storage
device which is stored on a dynamically mapped virtual memory data storage
subsystem having a rewriteable memory space, which device backup method is
extant on a data processor connected to the data storage subsystem which
is operational to instantaneously create a copy of a selected device
independent of said data processor, said device backup method comprising
the steps of:
allocating memory in said rewriteable memory space for a selected device
written thereon as well as for a copy of said selected device;
transmitting control messages to said data storage subsystem to identify
said selected device, and memory space for said copy of said selected
device;
activating said data storage subsystem to implement said instantaneous copy
operation on said identified all data sets which comprise said selected
device; and
updating, in response to said data storage subsystem copying said selected
device, meta data associated with said device and known by said data
processor, comprising:
updating at least one of device data comprising: Volume Table of Contents
(VTOC); Volume labels; VTOC index; Virtual Volume Data Set (VVDS) data.
14. The device backup method of claim 13 wherein said step of allocating
memory comprises:
determining a location and an extent of said selected device.
15. The device backup method of claim 13 wherein said step of allocating
memory comprises:
determining a location and an extent of said copy of said selected device.
16. The device backup method of claim 13 wherein said step of transmitting
control messages comprises:
transmitting data to said data storage subsystem to identify a location and
an extent of said selected device, and a location and an extent for said
copy of said selected device.
Description
FIELD OF THE INVENTION
This invention relates to data storage subsystems, and, in particular, to
an MVS device backup system which is resident on a data processor and
which regulates the backup of an MVS device on to the virtual data storage
devices of a data storage subsystem which is connected to the data
processor. The MVS device backup system manages the designation of the
source and target data storage volumes and activates the snapshot copy
resources of the data storage subsystem to perform the device backup
operation without the necessity of the data processor having to expend a
significant amount of processing resources.
PROBLEM
It is a problem in the field of computer systems to efficiently create
backup copies of the data sets of an MVS device, which backup copies
represent a single point-in-time for all data resident on the source MVS
device. In a typical computer system, data processors are connected to one
or more data storage subsystems, which include disk drive memory systems.
The data processors and their associated data storage subsystems therefore
must manage the backup of data sets stored on the virtual volumes of the
data storage subsystem in a manner that does not adversely impact the
performance and efficiency of the data processor and which also ensures
the integrity of the data.
The backup of device data in a traditional DASD data storage subsystem
entails the data processor retrieving the device data from the data
storage subsystem, then writing the retrieved device data to a designated
backup data storage location in the data storage subsystem. In particular,
as part of this process, device data backup utilities perform volume track
level backup by executing a series of read and write channel programs.
These channel programs read data from the data storage subsystem into
memory on a data processor and then write the data back out to the backup
data storage subsystem as a series channel programs from that data
processor memory. This system is resource intensive, in that the data
processor expends a significant amount of resources (CPU cycles) to
achieve the device data backup operation. In addition, channel resources
are needed to perform the data processor based device backup operation.
Furthermore, two significant difficulties with data storage subsystems are
the time required to make backup copies of device data and the need to
maintain the consistency of the device data during the time it takes to
make backup copies of the device data. This is a significant issue when a
backup copy must be made of a large devices which may contain many devices
or data bases which are the target of a single or common application
programs.
Several further problems are encountered in the creation of backup copies.
The creation of physical backup copies of device data requires the
expenditure of data processor, data channel, data storage subsystem and
backup data storage device resources. In addition, the concurrent access
to the device data may be hindered due to device request queuing. This is
necessitated by the requirement that the backup data represents a single
point-in-time copy of the data for the entire source device.
An alternative to the data processor controlled device copy operation
described above is the data storage subsystem snapshot copy operation
described in U.S. Pat. No. 5,410,667. This snapshot copy system creates a
duplicate device pointer in a virtual track directory in the data storage
subsystem to reference a device that a data processor has requested the
data storage subsystem to copy. This enables the data processor to access
the device via two virtual addresses while only a single physical copy of
the device resides in the data storage subsystem. The snapshot copy
operation is effected without the involvement of the data processor, since
it is managed solely within the data storage subsystem. However, the
snapshot copy operation cannot be selected by the data processor, but is
because it is solely within the purview of the data storage subsystem. In
addition, the snapshot copy operation is not available for use in creating
a backup copy of an MVS device.
SOLUTION
The above described problems are solved and a technical advance achieved in
the field by the MVS device backup system of the present invention which
functions to enable the data processor to manage the device backup
function in a manner that minimizes the expenditure of data processor
resources. This is accomplished by the MVS device backup system
designating the source and destination device volumes and then activating
the snapshot copy resources of the data storage subsystem to perform the
device backup operation without the necessity of the data processor being
involved in the execution details of the operation. In addition, the
instantaneous creation of a backup copy of the device data maintains a
point-in-time image of the device data from the initiation of the device
backup process until a physical backup copy of the device data is
available.
The implementation of the MVS device backup system is data processor based,
yet the DASD volume device backup is performed without using data
processor CPU resources to perform the actual movement of the device data.
Thus, the traditional data reads to data processor memory and the write
channel programs are not utilized to copy the device data from a source
device location to a target (backup) device location. Instead, the MVS
device backup system determines the source device volume on the data
storage subsystem, the target device volume on the data storage subsystem
and identifies the extents of both. The MVS device backup system then
transmits data to the data storage subsystem, representative of the
assignment of DASD full tracks from the source device location on the data
storage subsystem as well as DASD full tracks from the target (backup)
device location on the data storage subsystem. The data processor based
MVS device backup system then uses Extended Channel Access Method (ECAM)
channel programs to instruct the data storage subsystem to perform the MVS
device backup operation using the data storage subsystem snapshot track
pointer copy operations. Upon conclusion of the device backup operation by
the data storage subsystem, the MVS device backup system updates the meta
data required to complete the device backup operation. Meta data is the
supporting volume and device structures, stored in the data processor,
that identify the devices and maintain the device status.
This MVS device backup system is a significant departure from the prior art
operation of data storage subsystems since it does not require the
expenditure of a significant amount of the data processor resources. In
addition, the existing data storage subsystem snapshot copy capability is
used to enable the data processor to control the copying of device data to
designated backup data storage locations.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 illustrates in block diagram form the overall architecture of a data
system which includes the MVS device backup system of the present
invention; and
FIG. 2 illustrates in flow diagram form the operational steps taken by the
MVS device backup system.
DETAILED DESCRIPTION
FIG. 1 illustrates in block diagram form the overall architecture of a
computer system 1 that incorporates the MVS device backup system BS of the
present invention. The computer system 1 includes at least one data
processor 11 to which are connected at least one data storage subsystem
(DSS) 3, 3' that contains at least one and likely a plurality of data
storage devices DS1-DS4 for reading and writing data onto data storage
media for use by the data processor 11.
The data storage subsystem 3, 3' comprises a dynamically mapped virtual
device data storage subsystem which implements a plurality of virtual data
storage devices. In the preferred embodiment of the invention disclosed
herein, the data storage subsystem 3 comprises a disk drive array data
storage subsystem, although any data storage technology can be used to
implement the data storage subsystem 3. For the purpose of simplicity of
description, the disk drive array data storage subsystem example is used
herein.
Mapping Tables
The data storage subsystem 3 dynamically maps between three abstract
layers: virtual, logical and physical. The virtual layer functions as a
conventional large form factor disk drive memory. The logical layer
functions as an array of storage units that are grouped into a plurality
of redundancy groups. The physical layer functions as a plurality of
individual small form factor disk drives. The data storage subsystem 3
effectuates the dynamic mapping of data among these abstract layers and
controls the allocation and management of the actual space on the physical
devices. These data storage management functions are performed in a manner
that renders the operation of the data storage subsystem 3 transparent to
the data processor 11, which perceives only the virtual image of the data
storage subsystem 3. A virtual device is therefore an entity addressable
by data processor 11, with data processor-controlled content and data
processor-managed space allocation. In this system, the virtual device
consists of a mapping of a large form factor disk drive image onto a
plurality of small form factor disk drives which constitute at least one
redundancy group within the disk drive array. The virtual to physical
mapping is accomplished by the use of a Virtual Device Table (VDT) entry
which represents the virtual device. The "realization" of the virtual
device is the set of Virtual Track Directory (VTD) entries, associated
with the VDT entry each of which VTD entries contains data indicative of
the Virtual Track Instances, which are the physical storage locations in
the disk drive array redundancy group that contain the data records. The
data storage management functions are performed in a manner that renders
the operation of the data storage subsystems 3, transparent to data
processors 11.
Device Snapshot Copy Operation
As described in U.S. Pat. No. 5,410,667, the data storage subsystem 3
includes a device copy capability which is termed a "snapshot copy"
operation. The device snapshot copy operation instantaneously creates a
second instance of a selected device by merely generating a new pointer to
reference the same physical memory location as the original reference
pointer in the virtual track directory. In this fashion, by simply
generating a new pointer referencing the same physical memory space, the
device can be copied. A physical copy of the original device can later be
written as a background process to a second memory location, if so
desired. Alternatively, when one of the programs that can access the
device writes data to or modifies the device in any way, the modified
track is written to a new physical memory location and the corresponding
address pointers are changed to reflect the new location of this rewritten
portion of the device.
This apparatus therefore instantaneously copies the original device without
the time penalty of having to copy the track to the data processor 11 and
then write the track to a new physical memory location on the data storage
subsystem 3 via data channel 21. For the purpose of enabling a program to
simply access the track at a different virtual address, the use of this
mechanism provides a significant time advantage. In this fashion, a track
can be instantaneously copied by simply creating a new memory pointer and
the actual physical copying of the track can take place as a background
process without the involvement of the data processor 11.
Operation of MVS Device Backup System
FIG. 2 illustrates in flow diagram form the operation of the MVS device 10
backup system BS, as implemented in the system environment described
above. The MVS device backup system BS is illustrated herein as a device
management process using the snapshot track level subsystem copy facility
which is extant on the data processor 11, although other implementations,
such as merging the functionality of the MVS device backup system BS into
the other software running on data processor 11, are possible. In
operation, data processor 11 requests the creation of a backup copy of an
MVS device at step 201, which MVS device comprises a plurality of volumes
of data sets stored on a virtual device on a one (for example DSS 3) of
the data storage subsystem connected to data processor 11. The MVS device
backup system BS, in response to the receipt of a device backup request,
which includes an identification of the selected (source) MVS device,
locates the identified source MVS device at step 202 and serializes the
device staging request. The MVS device backup system BS searches the DSCB
entries of the Volume Table of Content (VTOC) available to the data
processor 11 and executes device type queries where necessary to thereby
determine the device characteristics of the identified source MVS device
as designated by the data processor 11. However, the data storage
subsystem 3 stores data for the data processor 11 in virtual volumes, a
plurality of which are implemented in data storage subsystem 3, as for
example 256 logical DASD volumes. Thus, the device location information
obtained by the MVS device backup system BS comprises the data processor
view of the data storage location in which the selected source MVS device
is stored on data storage subsystem 3.
The MVS device backup system BS, in response to the receipt of a device
backup request, also locates or allocates a target location for the
storage of the copy of the selected source MVS device at step 203. The MVS
device backup system BS searches the DSCB entries of the VTOC available to
the data processor 11 and executes device type queries where necessary to
thereby determine the physical location of available memory space of
sufficient extent to store the copy of the identified source MVS device.
In addition, the selection of the online candidate backup device can be
accomplished by user request or automatically selected based upon device
usage criteria. The MVS device backup system BS typically queries the
backup device to determine relevant information regarding the present
state of this device, including device label, device characteristics,
available memory, and the like. Once the backup device has been selected,
the device is serialized by the MVS device backup system BS. The data
storage subsystem 3 stores data for the data processor 11 in virtual
volumes, a plurality of which are implemented in data storage subsystem 3
and the device location information obtained by the MVS device backup
system BS comprises the data processor view of the data storage location
in which the copy of the selected device will be stored on data storage
subsystem 3, if data storage subsystem 3 is the target device for storage
of the backup copy of the identified MVS device.
Once the source and target locations are identified, the MVS device backup
system BS, at step 204, builds a set of ECAM channel programs to activate
the copying of the identified source MVS device, and the associated
creation of track pointers. In operation, the MVS device backup system BS
creates an ECAM channel message for each extent of tracks that are to be
copied in the identified source MVS device. These ECAM messages are
submitted serially to the data storage subsystem 3 to effect the device
backup operation. In particular, the MVS device backup system BS issues an
ECAM source definition message to the data storage subsystem 3 to define
both the Source and Target Locations as well as the Extent for both of
these locations. The MVS device backup system BS transmits the ECAM source
definition message to the data storage subsystem 3 over the data channel
21 which connects these two systems in well known fashion. The ECAM source
definition message is used to prepare the data storage subsystem 3 for the
execution of the device snapshot copy operation and also functions as a
security measure. The security aspect of the process involves the passing
of a token at step 205 from the data storage subsystem 3 to the MVS device
backup system BS to tie the received data with future instructions
received from the MVS device backup system BS. In response to the receipt
of the ECAM source definition message, the data storage subsystem 3 stores
the received Source and Target Location data as well as the Extent data
for future use.
The MVS device backup system BS at step 206 generates an ECAM Target
Execution message which instructs the data storage subsystem 3 to execute
the requested MVS device backup operation, using the Source and Target
Location, and Extent data received in the previous ECAM source definition
message. This message is tied to the previously transmitted ECAM source
definition message by the inclusion of the token which was received from
the data storage subsystem 3 in the previously executed ECAM source
definition message exchange. The data storage subsystem 3 uses the token
included in the ECAM Target Execution message to identify the stored
Source and Target Location and Extent data to perform the MVS device
backup operation in well known fashion. Since the data storage subsystem
snapshot copy operation executes independent of the data processor, the
data storage subsystem 3 returns an MVS device backup acknowledgment
message, including a polling token, at step 207 to the MVS device backup
system BS on data processor 11. This polling token enables the MVS device
backup system BS to query the data storage subsystem 3 to ascertain the
completion status of the MVS device backup process, which physical copy is
created as a background process, as noted above.
The MVS device backup query is implemented via the use of an ECAM Status
Inquiry message, which comprises a status inquiry message. The MVS device
backup system BS inserts the polling token in the ECAM Status Inquiry
message to identify the particular device snapshot copy operation of
interest (which represents the MVS device backup) and transmits the
message at step 208. The data storage subsystem 3 responds to a received
ECAM Status Inquiry message by returning a response at step 209 indicative
of snapshot copy (MVS device backup) completed status. The MVS device
backup system BS can originate as many ECAM Status Inquiry messages as
needed until the data storage subsystem 3 transmits a response to the ECAM
Status Inquiry message which indicates successful completion of the device
snapshot copy (MVS device backup) operation.
Once the MVS device backup operation is completed, the MVS device backup
system BS at step 210 must update the meta data associated with the Target
backup MVS device. The meta data comprises: VTOC; Volume labels; VTOC
index; Virtual Volume Data Set (VVDS) data, which is data processor 11.
The MVS device backup system BS updates this data in well-known fashion to
accurately reflect the location and extent of both the source MVS device
as well as the backup copy of the MVS device created by the device
snapshot copy operation of the data storage subsystem 3. Once the MVS
device backup system BS updates the meta data, the MVS device backup
system BS forces device recognition processing to be activated for the
backup MVS device, which thereby allows concurrent access to both the
source MVS device and the backup MVS device. At this juncture, the MVS
device backup operation is completed and processing exits at step 211.
SUMMARY
The MVS device backup system therefore functions to enable the data
processor to manage the device backup function of a disk data storage
subsystem in a manner that minimizes the expenditure of data processor
resources. This is accomplished by the MVS device backup system
determining the source MVS device on the data storage subsystem, the
target MVS device on the data storage subsystem and identifying the
extents of both. The MVS device backup system then transmits data to the
data storage subsystem, representative of the assignment of DASD full
tracks from the source MVS device location on the data storage subsystem
as well as DASD full tracks from the target MVS device location on the
data storage subsystem. The data processor based MVS device backup system
then uses ECAM channel programs to instruct the data storage subsystem to
perform the MVS device backup operation using snapshot track pointer copy
operations. This eliminates the need for the data processor to be
intimately involved in the execution of the MVS device backup operation.
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